/Engine/Source/Runtime/Engine/Public/GeomTools.h
Take a set of 3D Edges and project them onto the supplied plane. Also returns matrix use to convert them back into 3D edges.
namespace FGeomTools { void FGeomTools::ProjectEdges ( [TArray](API\Runtime\Core\Containers\TArray)< [FUtilEdge2D](API\Runtime\Engine\FUtilEdge2D) > & Out2DEdges, FMatrix & ToWorld, const [TArray](API\Runtime\Core\Containers\TArray)< [FUtilEdge3D](API\Runtime\Engine\FUtilEdge3D) > & In3DEdges, const FPlane & InPlane ) }